In the case of a known device for coating pills of this kind, larger drums are mostly supported via crown bearings, namely two annular rails are mounted on the periphery of the drum at both ends, these rails being rotatably supported on bearing rollers fastened to the base. The operation of such drums however have various disadvantages. For one, the rotation produces constant wobbling resulting in uneven coating. In addition to that, since the running speed at the bearing point is relatively high due to the large diameter of the drum, the operation of the drum causes to constant, disturbing noise.
In order to avoid that, smaller drums of such apparatus were supported overhung at one end (German open application No. 28 05 801), whereby at the opposite frontal end of the drum a closable loading opening is provided. Various advantages regarding the loading and unloading derive from this construction and the support can be achieved in this case with two relatively small roller bearings mounted relatively close to each other, without having to absorb substantial axial forces or tilting moments.
In order to continuously lower the processing and manufacturing costs of pills and comparable pharmaceutical products, as well as sweets, lately larger and larger drums are used, which have to be supported at both frontal ends in pivot bearings (German open application No. 31 31 808). The rolling effect, the layer height, the drying action and many other characteristics vary with the diameter of the drum and therefore the length of the drum is selected correspondingly dimensioned. This leads in the case of reasonable and economical constructions, respectively a light construction of the drum, to deflection, meaning that the duct connections laterally molded to the drum and respectively the support hubs become tilted with respect to the horizontal. High edge pressures result with slide bearings or even regular roller bearings and the use of self-aligning bearings is here too expensive. On the other hand, the use of roller bearings is preferred due to reduced resistance to rotation and the improvement of hygienic conditions.